Alkaline phosphatases are commonly used in routine biochemical procedures to remove phosphate groups from the terminus of a nucleic acid molecule. For example, calf intestinal alkaline phosphatase is a heat labile enzyme which is used to remove such phosphate groups, and then is inactivated by exposure to a high temperature. This thermal instability is advantageous because the alkaline phosphatase need not be removed from the reaction mixture prior to subsequent manipulations.
Alkaline phosphatase is also used as a non-radioactive marker for the detection of specific protein or DNA targets. It is conjugated to proteins or DNA oligonucleotides to aid in detection of such targets. Enzyme thermostability is desired in these applications. Alkaline phosphatases from various thermophilic and other organisms are known. Yeh et al., "Purification and Characterization of a Repressible Alkaline Phosphatase from Thermus aquaticus", J. Biol. Chem. 251:3134, 1976; Hartog et al., "An Alkaline Phosphatase from Thermus sp Strain Rt41A", Int. J. Biochem., 24:1657, 1992; Schaffel et al., "Alkaline Phosphatase from Bacillus licheniformis", Biochimica et Biophysica Acta, 526:457, 1978; Hulett-Cowling and Campbell., "Purification and properties of an alkaline phosphatase of Bacillus licheniformis," 10 Bioc. 1364, 1971.